Liquid meter



NOV. 18, 1952 H, H Fs 2,618,245

LIQUID METER Filed June 28, 1949 2 SHEETS--SHEET 2 Attorney 3 Patented Nov. 18, 1952 OFFICE LIQUID METER Hugh Edmund Phillips, Streatham Vale, London, England Application June 28, 1949, Serial No. 101,781

In Great Britain May 5, 1949 3 Claims.

This invention relates to liquid meters of the kind having pistons which are moved axially under the influence of the supply pressure and are rotated as a consequence of such axial movement.

' Meters of that kind comprise a pair of pistons arranged side by side and geared for rotation together. Each piston has a number of axial bores which can be made to communicate with feed or supply and deliverypassages through radial passages in the pistons which terminate in openings or ports through which the supply and delivery take place. The bores proceed from the ends of the pistons but have blind ends within the pistons so that when liquid under pressure is passed through a port and its associated bore into the cylinder space at one end of the piston, the piston is moved towards the other end of the cylinder an the liquid in the cylinder space at that end is expelled. The pistons are caused to rotate, or oscillate as a result of their axial movement so that the ports are brought cyclically into communication with the source of supply of the liquid to be metered and with a delivery passage. tional movements of the two pistons are out of phase with each other.

At different times during the operation of the meter, the ports are fully covered and fully uncovered by lands which separate the supply circuit from the delivery circuit. At no time, however, must the ports be fully covered longer than momentarily because the pistons are continuously reciprocated and the reciprocation is accompanied by a pumping action which makes it necessary that the liquid should at all times have freedom of movement. Also, no port'must at any time be in communication both with the supply circuit and the delivery circuit. Consequently, the machining of the ports and of the lands is a precision operation which makes these meters expensive to manufacture.

The object of the invention is to eliminate this criticality of the size of the ports and lands and thus to simplify and cheapen the cost of manufacture.

'To ensure that the ports are never in communication both with the supply circuit and with the delivery circuit is simple as it involves only making the lands larger than the ports. 'Io do'so, however, causes the ports to be fully covered for a period depending upon this difference in size. While the ports are fully covered, axial movement of the piston causes pressure to be built up at one end of the piston and rare- Both the axial and the rotafaction at the other and this will stop the movement of the piston and, therefore, the functioning of the meter, unless the liquid can leak past the piston, in which case, the metering efficiency is impaired.

, According to the invention, means are provided which automatically relieve the pressure and the rarefaction caused by complete covering of the ports, without interfering with the quantity of liquid delivered by the meter.

When such means are provided, the relative size of the lands and the ports is not critical. It is necessary only to ensure that the lands are greater than the ports so that a port cannot be simultaneously in communication with the supply circuit and the delivery circuit. The relative. size of the lands and ports will alter the'rating of the meter so that the latter has to be calibrated accordingly, but this is of no consequence having regard to the benefit to be derived from its being no longer necessary to match the ports and the lands accurately.

The relieving or compensating means which are provided in accordance with the inventioncan be of a very simple nature. They preferably consist of a, bore which extends through the piston from the supply end to the delivery end having in it a plunger which is a good sliding fit in the bore. increases, the plunger is moved in the bore so as to increase the volume of the space occupied by the liquid. Increase of pressure on one side is accompanied by decrease of pressure on the other and the movement of theplunger decreases the volume of the space occupied by the liquid on the latter side.

The arrangement just described is a particular example of the general case in which the two,

ends of the cylinder are connected by a passage by-passing the piston and containing a movable abutment which may be in the form of a floating piston or plunger or a diaphragm.

The adjustment of the "cylinder space at each end effected by the movement of the plunger or other pressure compensating means allows the piston to move in spite of its ports being fully When the pressure on one side delivery port has been closed, the pressure on" the delivery side increases and the plunger is forced backwards. the dead centre position i. e. changes its direction of movement, the delivery port being still closed, the pressure on the delivery side decreases and the movement of the plunger is reversed. The port, therefore, must not remain closed after the piston has passed throughthe dead centre position for a period longer than that. during which it remained closed before the dead centre position was. reached. To guard against this eventuality, the. port is preferably deliberately made to open nearer the instant at which the piston passes the dead centre position than. it is made to. close.

. It will be appreciated that,. a delivery port having been closed, on its being re-opened, it becomes a supply port which,.aft'er beingclosed is re-opened as a deliveryport. The same. considerations as to timing of opening andclosing of. a supply port as those explained above arise in connection with the delivery port:

In order that the invention may be thoroughly understood and'be more readily carried into effect,

an exampl'eo fameter'in accordance with it will noW'be described: with. reference to the accoma panying drawings in which:

Figs. 1, 2 and 3 are" cross sectionsthrough the meter showing different'phase: of its operation.

Figs. 4;, 5 and 6 are'sections takenrespectively on the lines IV-IV, V--V' and VIVI .in Figs. 1, 2 and 3 and Figs. 7 and 8 are developments of the two cylinders of the meter showing the positions ofthe ports relatively to the supply and delivery passages at various instants.

A meter of the kind shown in the drawings has a casing H0 in which are formed two cylinders I 12 each housing a piston H4. The cylinders are fittedwith liners I28 one having-four slots, 4:;12, c and dand the other four'simil'ar slots e; f,- g and h'. The slots are separated by lands I, m and n and'o, p, q, r.

The slots at and' e communicate with a common supply'passage N8; the slots b and f communicate with a common delivery passage I242 A passage I65 in each piston establishes communication at all times between the slot 11 and thes-lot' c1 and between the slot e and the slot 9; a: similar passage I66 establishes corresponding communication between the slot. b and'the" slot (1 and between the slot f' and the slot 71:. This ensures thatthe radial thrusts on' the pistons" are always; balanced.

Each piston. has acrank pin I42 which fits in a; bearing, I38 carried by pinions I3ZWhiCh mesh with a commonpinion I34.

Each piston has two bores I46 and I 48 running fromopposite ends andterminating in ports 7 w, x, 'J and z in the peripheral surface of thepistons.

The meter operatesas follows: Considering first the left-hand piston H4 which is shown in Figs. 1 and 4 in its mid-stroke position. Liquid is supplied from the passage As the piston passes through H8 through the slot a and the port w into the bore I45. The piston is thereby driven upwards as seen in Fig. 4 and liquid is forced out of the space I10 in the cylinder through the bore I48, the port :0 and the slot b into the delivery passage I24. In so moving, the piston causes the crank pin I 42 to gyrate so that the piston is turned about itsaxis thus=bringing the ports w andzc opposite the'lands and Zasshownin Figs. 2 and 3.

The right hand piston which is shown in Figs. 1 and 4 at one end of its stroke is also reciprocated and'rotated by the pinions I32 and I34. Its reciprocation and rotation are both out of phase .With those of the left hand piston. While the ports of the left hand piston are being brought opposite the lands is and l, the ports 11 and z of the righthand piston are being brought opposite the slots e and 1. Liquid is therefore supplied from the passage I i8 to the bore I48 in the right hand piston as showninFig. 2 and that piston is moved-downwards asrseen. in Fig. 5. andliquid; is delivered to the passage I214 through. the bore I46. On reaching the end'of its stroke, the left hand piston reverses. its direction of movementwhil'e the ports wand .13 move past the lands k andl andopposite the slots b andc. Liquid is then. suppliedthrough the passage I65, the. slot cand the port. at. into the bore. I48 and'liquid isforced; out of the cylinder. space I68 throughthebore I46',.the port-w and. the slot bv into the delivery passage I24.

Meanwhile the rotation of'the right handi piston is reversed. but the axial movement continues downward (Fig.5) and the ports 1 and e, are. again covered by the lands. 0 and. p. On reaching the end of. its stroke,. the. right hand piston reverses its. direction of i movement but; its rotation continues so that the ports y andz move past. the lands o and p and opposite. the slots and 9. Liquid is then. suppliedithrough thepassage I65, the slot g,.the ports to the bore I45 andliquid is delivered through. the bore I48,.theport 1! and the slot [to thedelivery passage. I24.

Theleft hand piston completes its downward stroke, while the ports 1 anda: are; beingsbrought. back opposite the lands is andI. Duringthe first half. of the upward stroke, the. ports w and a: are brought past thelands. 7c andl. and opposite the. slots 6 and 1 so. thatagain liquid is delivered. through the port minto the passage I14. This completes one cyclev of the left handpistonc At the same time, the right handpistonmakesthe second half. of itsupward. stroke while the ports y and. z are brought pastthe 1ands.o;:and. p. This completes one cycle ofv the right handpiston. At all times, one'or'the other of the. pistons is being driven by the supply pressure and is driving the other through the pinions I34 and I32; at all times also, one or the other of the pistons is delivering'liquidthrough the passage I24.v

It-will be seen thatthe ports w, a: and 1/, aare more narrow than the lands. is, l and o,v p and therefore, that they will be covered by thelands. for periods corresponding to the difference in widths. When the ports are completely covered, no. liquid can pass through a cylinder buti as-the pistons are continuously reciprocated, there is aconstant. pumping action. Ordinarily, the pressure set up atone end of the cylinder would stop the-meter from operating and a: difference between the widths oi the ports and lands is not. permissible. Indeed, the ports and lands have tobe extremely accurately matched and this leads to a considerable manufacturing cost.

The necessity for such accurate matching is avoided accordin to the invention by the provision in each piston of a bore 200 running from end to end and containing a plunger 202. When the ports of a piston are completely covered and the piston is moved axially, no liquid is supplied to or. withdrawn from the end spaces I68 and I in the cylinder although the volume of those spaces is being altered. The surplus liquid at one end and the deficiency at the other end are catered for by movement of the compensating plunger 202 which is subjected to different pressures at its two ends. never subjected to a pressure which cannot be overcome by the supply pressure.

When a piston is delivering liquid, it is sub- The piston is, therefore,

jected to the supply pressure at one end, and the delivery pressure at the other and the compensating plunger 202 will, therefore, be at the end of the piston. In order that it may not be projected beyond the end of the piston, stops 204 are provided at each end of the piston. When, before the end of the stroke the delivery port is closed by a land, the compensating plunger 202 is moved back into a position such as that shown in chain lines on the left hand side of Fig. 5. On reversal of the movement of the piston, the port being still covered, the plunger is moved towards the rear end of the piston. If now the port were to remain covered for a period after the piston had reached its dead centre position longer than that during which it remained covered before that position was reached, the plunger would have to make a greater movement than it had previously made and would be pressed hard against its stop 204 and fail to exert its compensating action. It is therefore deliberately arranged that the lands cover the ports for a shorter period after reversal of the piston than before reversal. This is done by stepping the lands as shown in Figs. 7 and 8.

In those figures, the liners I28 are shown developed. The circles s and t represent the loci of the crank pins I42. The ports w, :c, y and z are shown in the positions they assume in the positions 1-8 of the crank pins and have been marked with corresponding numerals. Thus w indicates the position of the port w when the crank pin is in position 1, i. e. in the position shown in Fig. 1; 111 indicates its position when the crank pin is in position 4, i. e. in the position shown in Fig. 3; and so on. The single hatching indicates the existence of communication with the feed circuit; the double hatching indicates communication with the delivery circuit.

The left hand piston reverses in positions 3 and 7 of its crank pin. It will be seen that the lands is and Z (or the slots a, b, and c) are stepped at u. so that the port 111 is cut off from the supply in position 2 of the crank pin and is opened to delivery in position 4. Position 2 is further from the dead-centre or reversal position 3 than is position 4. Similarly, position 8 is nearer the dead-centre position '7 than is position 6. As explained above, this ensures that the plunger 202 is always effective.

It will be noted also, that the port 20 shut off from communication with the feed circuit (position 10 a little sooner than the port as is shut off from communication with the delivery circuit (position :0 The same applies to the ports 1 and a. If the opposite occurred, that is to say, communication with the delivery circuit were cut I pressure.

being metered.

oil before communication with the feed circuit had been cut off, an undesirable pressure would be built up in the cylinder space I10 (Fig. 4) before the plunger 202 could operate to relieve the A pulse would, therefore, be set up in the liquid circuit. This can be avoided by ensuring simultaneous cutting-01f of the communica tion with the feed and delivery circuits. Such a measure calls for very accurate machining but is not an essential one and is avoided by the provision of the compensatin plunger and by deliberately causing the communication with the feed circuit to be cut off first. The time lag between the two cutting-01f operations is not very material.

As already stated, the invention has the advantage of agreat simplification in the manufacture of the meter as it makes the formingot the supply and delivery slots a straight-forward machining operation requiring only ordinary good class tolerances instead of a high precision operation. It also eradicates a fundamental fault in meters of this kind which, in order that they might work at all, have previously necessarily had to provide some degree of leakage past the pistons.

The compensating plunger must be a good practically leak-proof fit. The expedient used to provide such a fit will depend upon th liquid Greater precaution must, of course, be taken when metering thin liquids of high penetrative power such as petrol than when metering thick liquids such as lubricating oil.

v In general, it is not necessary to take elaborate precautions, a number of sealing grooves being adequate.

I claim:

1. A liquid meter comprising a pair of cylinders each having an inlet port and an outlet port in it periphery, a pistonin each cylinder having an inlet port and an outlet port in its periphery and passages leading from said ports to opposite ends of the piston whereby liquid supplied through the inlet port in one of said cylinders [into the inlet port of the associated piston will cause said piston to be moved axially in said cylinder, means interconnecting and causing said pistons to rotate as a consequence of their axial displacement and thereby to bring the inlet and outlet ports in each piston successively into and out of communication with the inlet and outlet ports in the associated cylinder, said ports being so relatively disposed that there is a period during which the inlet and outlet ports in each piston are simultaneously sealed against communication with the inlet and outlet ports in the associated cylinder, each of said pistons having a. passage extendin from end to end thereof and out of communication with the ports in said pistons, a plunger in each passage freely movable therein under the influence of the fluid pressures acting on the ends of the pistons consequent upon said simultaneous sealing of said inlet and outlet ports and continued axial displacement of the associated piston, each of said pistons also having stops positioned so as to provide complete freedom of movement of said plunger during said period of simultaneous sealing of said ports but effective to limit said movement at other times.

2. A liquid meter as claimed in claim 1 in which said ports are so relatively disposed that said period of simultaneous sealing of said inlet and outlet ports persists while the direction of axial movement of the piston changes and said period starts at an instant which precedes that at which said-1 change takeszplaoeebyf a; greater. interyal. of; time:--

the: intern/at by: which the. instant; at which? said? period: ends; follows saidv instant: of?

changes. r

Alliquid metencomprising a pair of cylinderseach; having: an inlet port; and an outlet poi-tin its: periphery,., a. pistonin each. cylinder; having: aminlet port; and an'outlet portin its'periphery: and; passagexleading-fromv said ports to opposite: ends of the? piston whereby liquid suppliedthrough; the inlet: port-.in one of said cylinders" into the: inlet: port at: the associated piston: will causesaid: piston tohev moved: axially in: said cylinder; means: causing said; pistons: to rotate; as a consequence of their axial displacement. and thereby to; bring the inlet and outlet ports, in each: piston successively into; and out of com: munication with theinlet. and outlet ports in the associatedcylinder, said ports being-so relatively disposedrthatthereis a period. during Whichthe' inlet; and outlet ports in each piston: are simultaneously sealed against communicationwith the inlet and; outletports; in the associated cylinder, arpassagein eachof said pistons: extending from endto end thereof and out. of communication 81, with. said ports: in: the pistons. and a. plunger in. each passage; freely: movableetherein: under the" influence of; the fluidpressuresiactingmrthesends of" the pistons, said ports being; so; relativehtidise posed that. said; period. of; simultaneous; sealing: of: said inlet. and. outlet: ports: persists.- while the direction of axial movement ofthezpistonchangefi and starts at an; instant: which precedes. that: at which said change takes placeby agreater: interval of time; than. the intervalv by: which; the instant. at; which said, period. ends fOllOWSifiid instantxof change.

HUGH: EDMUND." PHILEIRS.

REFERENCES GITED;

The following references are of record in the file of this patent:

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